Preheat oven to 350°F and grease a deep souffle dish with butter. If you don't have a souffle dish you can use an 8x8 baking dish.

Cut the French bread into 1-inch cubes. If you already have stale bread, great! If not, let it sit out to dry slightly, or bake at 300°F for 10–15 minutes until lightly crisp.

In a large bowl, whisk together eggs, sugar, milk, vanilla, cinnamon, and nutmeg until smooth. Layer the bread cubes in the prepared dish and pour the custard evenly over the top, pressing down gently so the bread absorbs the mixture. Let sit for at least 20 minutes before baking. (you can leave it up to overnight)

Bake uncovered for 45–55 minutes, or until the top is golden and the center is set but still soft. Remove from the oven and let rest for 15–20 minutes to allow the custard to firm up.

In a small saucepan, combine ½ cup whole milk and ½ cup heavy cream. Warm over medium heat until bubbles form around the edges — don’t let it boil.

In a separate bowl, whisk together 6 egg yolks and ½ cup sugar until smooth. Slowly drizzle a small amount of the warm milk mixture into the eggs while stirring constantly to temper them. Continue adding a little at a time until the mixture is warm and combined.

Pour the tempered egg mixture back into the saucepan and cook over low heat, stirring constantly, until the sauce reaches 180°F or coats the back of a spoon. Remove from heat and strain through a fine mesh sieve into a clean bowl. Stir in 1½ teaspoons bourbon and 1 teaspoon vanilla extract.

Cover and refrigerate until chilled. Serve the bread pudding warm with the cold burbon sauce drizzled over each portion.